Fluidic frequency discriminator



g- 26, 5 J. G. MCMILLAN 3,463,177

FLU IDI C FREQUENCY DI SCR I MTNATOR Filed Oct. 7. 1966 FIG. 2

OUTPUT a v INPUT FREQUENCY INVENTOR. JOHN G. McMlLLAN Q MAZA WZ ATTORNEY United States Patent 3,463,177 FLUIDIC FREQUENCY DISCRIMINATOR John G. McMillan, New Brighton, Minn., assignor to Honeywell Inc., Minneapolis, Minn., a corporation of Delaware Filed Oct. 7, 1966, Ser. No. 585,039 Int. Cl. F15c 1/08 U.S. Cl. 13781.5 4 Claims ABSTRACT OF THE DISCLOSURE A fluidic frequency discriminator comprising a bistable fluid amplifier, having its control ports connected to tuned chambers of different lengths. One of the chambers is adapted to receive a variable frequency input signal. An output from the discriminator is obtained only when the frequency of the input signal is between two predetermined frequencies dependent on the lengths of the tuned chambers.

The invention herein described was made in the course of or under a contract with the Department of the Army.

This invention relates to a frequency discriminator, and more specifically to a fluidic frequency discriminator.

It is known in the fluid amplifier art that small fluid streams can be used to control a larger fluid stream. More specifically, in a bistable fluid amplifier the smaller fluid streams deflect a larger fluid stream from one receiver port into another receiver port through interact-ion of the fluid streams, However, I have discovered that by altering the geometric structure of a bistable amplifier I can make a change in the frequency of a fluid input signal to cause deflection of the fluid stream from one receiver port to another receiver port.

Briefly, the present invention comprises a bistable fluid amplifier having a first tuned chamber for introducing a fluid or acoustic signal of varying frequency and a second shorter tuned chamber oppositely disposed from the first tuned chamber. When the frequency of the fluid signal in the first tuned chamber is increased, the fluid power stream of the bistable fluid amplifier transfers from one outlet leg to the other outlet leg, and when the frequency of the fluid signal in the first tuned chamber is increased still further the fluid power stream transfers back to the outlet leg from which it originally was flowing.

A more thorough understanding of my invention may be had by referring to the attached drawing in which FIG- URE 1 shows a pictorial view of my fluidic frequency discriminator, and FIGURE 2 shows the output signal of my fluidic frequency discriminator with an increasing input signal.

Referring to FIGURE 1 reference numearl generally depicts my fluidic frequency discriminator which is comprised of a housing 11 and a cover plate 12 shown, for purposes of description, as being composed of transparent material. Housing 11 has a power nozzle 13, a first tuned chamber 14 which is connected to a source of pressure pulses 9, a second tuned chamber 15 which is open to the surrounding media, an outlet passage 17 and an outlet passage 16. Chambers 14 and 15 are referred to as tuned chambers because their length determines the critical frequencies at which switching occurs in the fluid amplifier. Attached to outlet passage 16 is a vent passage 18 for exhausting excess fluid and attached to outlet passage 17 is a similar vent passage 19 for exhausting excess fluid. The passages are all machined in the housing 11, which has the coverplate 12 attached thereto by fastening means such as an adhesive or the like. Located on the end of outlet leg 16 is an outlet passage 20 for obtaining the fluid output signal from the fluid frequency discriminator 10. The source of pressure pulses 9 may be a device such as shown in the Ogeren application Ser. No. 341,235 filed Jan. 30, 1964 and assigned to the same assignee as the present invention.

Referring now to FIGUREZ, a plot of the output pressure P at passage 20 is shown as a function of the varying input frequency at chamber 14.

In normal operation of my device a fluid stream, designated by the reference character P flows through power nozzle 13 and into outlet leg 17. By applying a control signal comprising a train of fluid pressure pulses of less than a predetermined critical frequency f at first tuned chamber 14, the fluid stream continues to flow out passage 17. However, by increasing the frequency of the control signal at first tuned chamber 14 to a value above f,,, the fluid stream flowing from passage 13 transfers from outlet leg 17 into outlet leg 16 and flows out passage 20. The pressure of the fluid at the output passage 20 is denoted by P and in FIGURE 2 it is shown that fluid pressure P increases sharply as the fluid stream flows out passage .20. When the frequency of the fluid signal at the first tuned chamber 14 is increased to a second predetermined critical frequency f the fluid stream flowing out passage 16 is transferred back into outlet passage 17 causing a decrease in the pressure signal P at passage 20. In other words, by applying a signal of increasing frequency at the tuned chamber 14 of my frequency discriminator 10, I have caused the fluid signal to transfer away from outlet leg 17 into outlet leg 16 and then back again into outlet leg 17. It is not completely understood why the bistable fluid amplifier with the tuned chambers 14 and 15 behaves in the aforedescribed manner, but I have determined that the operation is dependent upon the lengths of my chambers 14 and 15. That is, the tuned chamber 14 of length L must be greater than the oppositely disposed tuned chamber 15 of length L I have also found that the length L affects the frequency f, at which the fluid stream transfers into passage 16 and that the length of the chamber L affects the frequency f at which the fluid stream transfers from the outlet leg 16 to the outlet leg 17. For example, increasing length L decreases the switching frequency f,, and decreasing the length L increases the switch-ing frequency f,,. Similarly increasing the length L decreases the frequency f while decreasing the length L increases the frequency f at which switching occurs.

A typical set of dimensions for the control ports which have been found to work satisfactorily are L =2 inches and L inch.

While I have shown and described a specific embodiment of my invention further modifications and improvements will occur to those skilled in the art.

I claim:

1. A fluidic frequency discriminator comprising:

a bistable fluid amplifier including a power nozzle for issuing a fluid stream, a first outlet passage for normally receiving said fluid stream, a second outlet passage, and first and second control ports;

a first tuned chamber of length L connected to said first control port;

a second tuned chamber of length L which is less than length L connected to said second control port; and

means connected to said first tuned chamber for supplying a variable frequency fluid signal thereto, said first and said second tuned chambers operable to cause said fluid stream to transfer from said first out let passage to said second outlet passage when the variable frequency signal reaches a first predetermined frequency dependent on length L and to transfer back to said first outlet passage when the variable frequency signal increases to a second predetermined frequency dependent on length L 2. The apparatus of claim 1 further including vent passages connected to said first and said second outlet passages.

3. In a frequency responsive device;

a second fluid receiver;

a power nozzle for normally directing -a fluid stream into said second fluid receiver;

first and second control nozzles for directing control signals against said fluid stream;

a first tuned chamber connected to said first control nozzle; and

means connected to said first tuned chamber for supplying a variable frequency fluid signal thereto so that when said variable frequency signal reaches a first predetermined frequency said fluid stream is transferred away from said second fluid receiver and References Cited UNITED STATES PATENTS Stern 137-815 Warren et a1 13781.5

Bowles 13781.5

Meier 13781.5

Swartz 137-815 M. CARY NELSON, Primary Examiner WILLIAM R. CLINE, Assistant Examiner 

